diff --git a/src/Microsoft.AspNetCore.Authentication.Core/AuthenticationSchemeProvider.cs b/src/Microsoft.AspNetCore.Authentication.Core/AuthenticationSchemeProvider.cs
index e56247e1..325d4993 100644
--- a/src/Microsoft.AspNetCore.Authentication.Core/AuthenticationSchemeProvider.cs
+++ b/src/Microsoft.AspNetCore.Authentication.Core/AuthenticationSchemeProvider.cs
@@ -59,7 +59,7 @@ public Task<AuthenticationScheme> GetDefaultAuthenticateSchemeAsync()
         /// <summary>
         /// Returns the scheme that will be used by default for <see cref="IAuthenticationService.ChallengeAsync(HttpContext, string, AuthenticationProperties)"/>.
         /// This is typically specified via <see cref="AuthenticationOptions.DefaultChallengeScheme"/>.
-        /// Otherwise, if only a single scheme exists, that will be used, if more than one exists, null will be returned.
+        /// Otherwise, this will fallback to <see cref="GetDefaultAuthenticateSchemeAsync"/>.
         /// </summary>
         /// <returns>The scheme that will be used by default for <see cref="IAuthenticationService.ChallengeAsync(HttpContext, string, AuthenticationProperties)"/>.</returns>
         public Task<AuthenticationScheme> GetDefaultChallengeSchemeAsync()
@@ -68,11 +68,7 @@ public Task<AuthenticationScheme> GetDefaultChallengeSchemeAsync()
             {
                 return GetSchemeAsync(_options.DefaultChallengeScheme);
             }
-            if (_map.Count == 1)
-            {
-                return Task.FromResult(_map.Values.First());
-            }
-            return Task.FromResult<AuthenticationScheme>(null);
+            return GetDefaultAuthenticateSchemeAsync();
         }
 
         /// <summary>
@@ -93,7 +89,7 @@ public Task<AuthenticationScheme> GetDefaultForbidSchemeAsync()
         /// <summary>
         /// Returns the scheme that will be used by default for <see cref="IAuthenticationService.SignInAsync(HttpContext, string, System.Security.Claims.ClaimsPrincipal, AuthenticationProperties)"/>.
         /// This is typically specified via <see cref="AuthenticationOptions.DefaultSignInScheme"/>.
-        /// Otherwise, if only a single scheme exists, that will be used, if more than one exists, null will be returned.
+        /// Otherwise, this will fallback to <see cref="GetDefaultAuthenticateSchemeAsync"/>.
         /// </summary>
         /// <returns>The scheme that will be used by default for <see cref="IAuthenticationService.SignInAsync(HttpContext, string, System.Security.Claims.ClaimsPrincipal, AuthenticationProperties)"/>.</returns>
         public Task<AuthenticationScheme> GetDefaultSignInSchemeAsync()
@@ -102,11 +98,7 @@ public Task<AuthenticationScheme> GetDefaultSignInSchemeAsync()
             {
                 return GetSchemeAsync(_options.DefaultSignInScheme);
             }
-            if (_map.Count == 1)
-            {
-                return Task.FromResult(_map.Values.First());
-            }
-            return Task.FromResult<AuthenticationScheme>(null);
+            return GetDefaultAuthenticateSchemeAsync();
         }
 
         /// <summary>
diff --git a/test/Microsoft.AspNetCore.Authentication.Core.Test/AuthenticationSchemeProviderTests.cs b/test/Microsoft.AspNetCore.Authentication.Core.Test/AuthenticationSchemeProviderTests.cs
index 3810f833..9fe65bd2 100644
--- a/test/Microsoft.AspNetCore.Authentication.Core.Test/AuthenticationSchemeProviderTests.cs
+++ b/test/Microsoft.AspNetCore.Authentication.Core.Test/AuthenticationSchemeProviderTests.cs
@@ -60,6 +60,24 @@ public async Task DefaultSchemesFallbackToOnlyScheme()
             Assert.Equal("single", (await provider.GetDefaultSignOutSchemeAsync()).Name);
         }
 
+        [Fact]
+        public async Task DefaultSchemesFallbackToAuthenticateScheme()
+        {
+            var services = new ServiceCollection().AddOptions().AddAuthenticationCore(o =>
+            {
+                o.DefaultAuthenticateScheme = "B";
+                o.AddScheme<Handler>("A", "whatever");
+                o.AddScheme<Handler>("B", "whatever");
+            }).BuildServiceProvider();
+
+            var provider = services.GetRequiredService<IAuthenticationSchemeProvider>();
+            Assert.Equal("B", (await provider.GetDefaultForbidSchemeAsync()).Name);
+            Assert.Equal("B", (await provider.GetDefaultAuthenticateSchemeAsync()).Name);
+            Assert.Equal("B", (await provider.GetDefaultChallengeSchemeAsync()).Name);
+            Assert.Equal("B", (await provider.GetDefaultSignInSchemeAsync()).Name);
+            Assert.Equal("B", (await provider.GetDefaultSignOutSchemeAsync()).Name);
+        }
+
         [Fact]
         public async Task DefaultSchemesAreSet()
         {